1. Soluble DPP-4 up-regulates toll-like receptors and augments inflammatory reactions, which are ameliorated by vildagliptin or mannose-6-phosphate
- Author
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Dae Ho Lee, Hyuncheol Oh, Dong-Sung Lee, Eun-Sol Lee, Dae-Gil Kang, Md. Morshedul Alam, Youn-Chul Kim, Jun-Hyeog Jang, Young Sang Koh, Ho Sub Lee, and Zahid Manzoor
- Subjects
Lipopolysaccharides ,0301 basic medicine ,medicine.medical_specialty ,Pyrrolidines ,Dipeptidyl Peptidase 4 ,Endocrinology, Diabetes and Metabolism ,medicine.medical_treatment ,Nitric Oxide Synthase Type II ,Adamantane ,Proinflammatory cytokine ,Mice ,03 medical and health sciences ,Endocrinology ,Internal medicine ,Nitriles ,medicine ,Animals ,Vildagliptin ,RNA, Messenger ,Receptor ,Cells, Cultured ,Inflammation ,Dipeptidyl-Peptidase IV Inhibitors ,Mannosephosphates ,biology ,Chemistry ,Kinase ,Toll-Like Receptors ,NF-kappa B ,Mice, Inbred C57BL ,Nitric oxide synthase ,TLR2 ,030104 developmental biology ,Cytokine ,TLR4 ,biology.protein ,medicine.drug - Abstract
Objective Studies have shown that dipeptidyl peptidase-4 (DPP-4) inhibitors have anti-inflammatory effects. Soluble DPP-4 (sDPP-4) has been considered as an adipokine of which actions need to be further characterized. Methods We investigated the pro-inflammatory actions of sDPP-4 and the anti-inflammatory effects of DPP-4 inhibition, using vildagliptin, as an enzymatic inhibitor, and mannose-6-phosphate (M6P) as a competitive binding inhibitor. Results In lipopolysaccharide (LPS)-stimulated RAW264.7 cells, vildagliptin suppressed the increased expression of inducible nitric oxide synthase (iNOS) and phosphorylated JNK (pJNK), activation of the NF-κB pathway, and the resultant NO and proinflammatory cytokine production. Although sDPP-4 alone did not affect the protein level of iNOS or pJNK or the production of NO in RAW264.7 cells, it did amplify iNOS expression, NO responses, and proinflammatory cytokine production in LPS-stimulated RAW264 cells. As a probable mechanism, we found that sDPP-4 caused dose-dependent increases in the expression levels of toll-like receptor 4 (TLR4) and TLR2 in RAW264.7 cells, and that these alterations were inhibited by vildagliptin, M6P, or bisindolylmaleimide II, a protein kinase C inhibitor. Either vildagliptin or M6P suppressed iNOS expression and NO and cytokine production in LPS + DPP-4-co-stimulated macrophages, while combined treatment of the co-stimulated cells with both agents had increased anti-inflammatory effects compared with either treatment alone. Intravenous injection of sDPP-4 to C57BL/6J mice increased the expression of both TLRs in kidney and white adipose tissues. Conclusion Our findings suggest that sDPP-4 enhances inflammatory actions via TLR pathway, while DPP-4 inhibition with either an enzymatic or binding inhibitor has anti-inflammatory effects.
- Published
- 2016
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